Broadly, this invention relates to turf reinforcement mats. Turf reinforcement mats, or TRM's promote revegetation, provide erosion protection and improve water quality on slopes and in channels. More specifically, the present invention relates to the polymer fiber filler material used in the construction of a permanent turf reinforcement mat. The polymer filler employed has multidimensional fiber cross sections.
Known turf reinforcement mats in the art are typically fabricated in one of the following three ways: (1) polymer monofilament or natural organic fibers are stitch bonded together; (2) polymer monofilament can be fused with netting or (3) polymer monofilaments are woven into erosion control structures.
The patent literature does include several attempts at producing a polymeric geotextile. For example, U.S. Pat. No. 3,934,421 discloses a matting comprising a plurality of amorphous thermoplastic filaments used for stabilizing road beds. The thermoplastic may be any melt-spinnable polymer, which is spun into loops about 10 times the diameter of the filament. Matting is laid flat on the ground where repeated traffic thereon sinks the matting below the surface. The thickness of the matting tends to fill with sediment thereby stabilizing the surface. The matting may also be used for drainage in wet road beds. The porosity of the matting acts as a moisture conduit, draining excess moisture into an otherwise provided adjacent drainage area. It is briefly noted that the filaments with a non-round cross section have a greater load bearing capacity than filaments with round cross sections. Hence, the thickness of a mat for a given load may be decreased when using non-round filaments relative to the load capacity of round cross section filaments.
U.S. Pat. No. 4,181,450 discloses an erosion control matting having an open mesh reinforcing lattice over which a plurality of continuous melt-spun polymer filaments are overlaid and interlocked with the lattice. This structure is positioned over a fibrous backing member intended to capture and retain soil. The polymers contemplated include polyolefins, polyesters, and polyamides.
U.S. Pat. No. 4,329,392 discloses a multilayer netting for hydraulic engineering and erosion control. One layer of the matting is a “gripper layer” containing melt-spun polymer filaments of a larger diameter fused to a plurality of intersecting melt-spun polymer filaments of a smaller diameter. The gripper layer is placed on and reaches into fine sediment particles, thereby interlocking with the surface to be protected from erosion. A “grain rearrangement inhibiting” fiber layer is interspersed in the voids of the gripper layer, and acts as a filter prevent escape of the finest particles.
U.S. Pat. No. 4,472,086 discloses a geotextile fabric comprising first and second groups of synthetic threads, the two groups disposed essentially perpendicular to one another. A third group of threads stitch-bonds the first two groups together loosely. Use of the geotextile fabric as asphalt road repair is disclosed.
U.S. Pat. No. 5,182,162 discloses a self-bonded non-woven web and thermoplastic net-like web composite comprising at least one layer of fibrous non-woven web, which itself includes radially disposed filaments and at least one layer of aligned thermoplastic elements. The fibers can be made from a variety of polymers including polyolefins such as polyethylene, polypropylene and polyesters, and are made by extruding through spinnerettes having cross sections that can be circular, elliptical, or tri-lobal. The net-like webs disclosed therein are suitable for use as a geotextile or agricultural ground cover and useful in controlling erosion.
U.S. Pat. No. 5,851,089 discloses a geogrid composed of multiple layers of flexible mesh structures. The layers are offset from one another such that the mesh openings are not superimposed. The multiple layers are fastened to one another, and the multilayer structure is stretched in either one direction, i.e., machine direction, or in two orthogonal directions, i.e., machine direction and transverse direction. Gaps in the resulting geogrid are of various sizes, ensuring that fill sediment of various sizes may infiltrate and firmly hold the geogrid in place. The geogrid is useful in reinforcement of paved and unpaved roads, and in preventing erosion and stabilizing fill material.
U.S. Pat. No. 6,171,984 discloses a meshwork used for erosion control and soil stabilization, wherein two sets of strands, orthogonally disposed to one another, are connected with at least one set of tying strands and a bonding agent. The strands may be made of thermoplastic or glass fibers. Use of fiberglass in the geosynthetic material improves its resistance to environmental and biological wear.
While attempts have been made heretofore to provide a turf reinforcement mat having improved drainage capability and tensile strength, the art has not provided a mat that provides improved revegetation, erosion protection and water quality on slopes and in channels.